This invention relates to a gas fireplace, and, in particular, to a gas fireplace adapted to provide heat to multiple zones of a building.
Known in the art are a multitude of different types of gas fireplaces, including gas fireplaces such as freestanding models and zero clearance models which provide heating to the room in which it is located. These fireplaces commonly include housings or shells that surround the combustion chambers or fireboxes where combustion of a gaseous fuel, such as propane or natural gas, occurs. The walls of the housing are typically constructed in spaced relationship with some or all of the walls of the combustion chamber, including the bottom wall and top wall which form the floor and ceiling of the combustion chamber. The resulting space or plenum provided between the combustion chamber and housing permits the formation of passageways suitable to circulate air. Existing fireplaces have used these passageways to circulate air to serve a number of nonexclusive purposes, including the transfer of heat to room air which is inlet into these passageways and circulated therethrough by means of natural convection or electric motor driven fans. The inlet room air is discharged from the fireplace at a higher temperature to heat only the room in which the fireplace unit is installed, with any heating provided by the fireplace to other rooms being incidental. Thus, buildings having previously known fireplaces are generally provided with a separate furnace or other heating means and, in some cases, an air conditioner for cooling or circulating air throughout the building incorporated into the separate furnace or standing alone.
Generally, present direct vent fireplaces have steady state efficiencies of up to approximately 75 percent, and Annual Fuel Utilization Efficiencies (AFUE) in the 60 to 65 percent range. Improvements in these efficiencies would, of course, be desirable, although it is recognized in the art that the steady state efficiency is limited to a maximum of 83 percent to prevent condensation in the flue in noncondensing applications. Generally, flue gas temperatures at the flue terminal should be about 190.degree. F. (87.8.degree. C.), or at least 50.degree. F. (27.degree. C.) above the dew point of the flue gases.
It is also desirable to provide a fireplace which serves an aesthetic function as well as providing heat to rooms or zones other than the zone in which the fireplace is installed in response to calls for heat from the remote zones, obviating the need for a separate furnace. With the fireplace taking the place of a furnace, it is desirable to also have the ability to provide the heated air and unheated or cooled air to the various zones through common air conveyance means. Moreover, in the event of electrical power failure, it is desirable that some quantity of heat still be provided to the various zones.